Ultrasonic rat elimination system having random modulation

ABSTRACT

Apparatus and method for repelling rats and mice from an area by means of generation of a modulated ultrasonic sound level. The sound level is frequency modulated within a range of ultrasonic frequencies to which rats and mice respond. In addition, it is amplitude modulated in a random manner. The modulations of the signal prevent rats and mice from adapting to the sound, and thereby renders the sound particularly unpleasant to them.

United States Patent Del Grande et all.

[451 Jan. 18, 1972 ULTRASONIC RAT ELIMINATION SYSTEM HAVING RANDOMMODULATION Inventors: Dominic Del Grande, North Hollywood;

Donald C. Erdman, Pasadena both of Calif.

The Rat Elimination System Limited, Nassau, Bahamas Filed: Nov. 18, 1968Appl. No.: 776,646

Assignee:

US. Cl ..340/384, 340/388 Int. Cl. ..G08b 3/10 Field of Search..340/384, 384 E References Cited UNITED STATES PATENTS 3/1958 Elliot..340/384 E 3,160,877 12/1964 Monomakhoff ..340/384 E 3,254,336 5/1966Campbell ..340/384 E 3,466,649 9/1969 Colman. ..340/384 E 2,922,9991/1960 Carlin.... 340/384 E 3,051,944 8/1962 Smith 340/384 E 3,165,7341/1965 Grodzinsky 340/384 E 3,173,136 3/1965 Atkinson... ..340/384 E3,196,432 7/1965 Kock ..340/384 E Primary ExaminerHarold l. PittsAttorneyChristie, Parker & Hale ABSTRACT Apparatus and method forrepelling rats and mice from an area by means of generation of amodulated ultrasonic sound level. The sound level is frequency modulatedwithin a range of ultrasonic frequencies to which rats and mice respond.In addition, it is amplitude modulated in a random manner. Themodulations of the signal prevent rats and mice from adapting to thesound, and thereby renders the sound particularly unpleasant to them.

PATENTEU JAN: 8 1372 ULTRASONIC RAT ELIMINATION SYSTEM HAVING RANDOMMODULATION BACKGROUND OF THE INVENTION This invention relates to thecontrol of pests and, more particularly, to an apparatus and method forrepelling rats and mice. Mice and, more particularly, rats, have longbeen recognized as carriers of disease and as extremely dangerous anddestructive pests. The common rat has, in fact, been called probably themost injurious and universal pest of the human race. An advantage of thepresent invention is that it is highly efficient in eliminating thesepests from an area in which this invention is used.

Prior attempts to control these pests have generally required the use oftraps with attendant fuss and bother with bait as well as dirty cleanupwork. Another advantage of the present invention is that it completelyeliminates the need for traps, bait and cleanup work.

Another advantage of the present invention is that it drives rats andmice from their habitat without killing them.

It has long been known that rats and mice are startled by high-frequencysound. The degree of reaction varies from a state of nervousness atlow-sound energies on up to audiogenic seizure when the sound level ishigher. Studies have shown that almost any frequency within the 20-40kHz. range will cause convulsion in rats if the sound level is in the130-140 decibel range. Such sound intensities are difficult to obtain inlarge areas such as grain storage areas or market places. Additionally,there is danger of the pests adapting themselves to a signal of constantfrequency or to a signal which follows a repetitive uniform pattern.

Yet another advantage of the present invention is that it repels ratsand mice by means of ultrasonic sound levels of lower magnitude thanthose heretofore thought to be required for the elimination of suchpests.

Yet another advantage of the present invention is that if repels ratsand miceby means of ultrasonic sound signals which do not follow auniform pattern to which the pests could acclimate themselves.

Still another advantage of the present invention it that it provides ahighly efficient method of eliminating and preventing the damage andhazards caused by rats and mice.

SUMMARY OF THE INVENTION In brief, the preceding and additional objectsare achieved by means of the production of ultrasonic signals which areconstantly modulated with respect to frequency. We have found thatstartle reactions and often clonic seizures can be induced in rats andmice at sound levels as low as ll20 decibels if the frequency of thegenerated sound is swept between l8.5 and 30 kHz. It is believed thatthe reactions obtained at such lower sound levels are achieved becausethe pests are unable to acclimate themselves to the changing frequencyof the signal. It has further been found that adding amplitudemodulation to the signal in a fairly random manner aids in preventingthe pests from adapting to and therefore ignoring the sound. Suchmodulation makes the sound extremely unpleasant. Signals within thesuggested frequency range are not only above the upper frequency limitto which human beings respond, but are also above the level to whichdogs, cats and other household pets respond.

In accordance with the present invention, rats and mice may beeffectively eliminated from an area of up to 10,000 square feet by meansof the generation of an electrical signal within the ultrasonicfrequency range; modulating the signal, by causing the frequency torepetitively sweep within a predetermined frequency range and bysimultaneously modulating the amplitude of the signal; and by thenconverting the electrical signal to air vibrations in order to producean ultrasonic sound level of at least 100 decibels. It is likely that insmaller areas a sound level of even less than 100 decibels may besufficient to eliminate rats therefrom.

In another embodiment, a speaker for converting the electrical signal toultrasonic sound is repeatedly switched on and off in order to providean interrupted output. This permits the speaker to cool off during theinterruptions in the output signal. The interruptions do not have anydetected effect upon the rat repelling action and, in fact, may indeedfurther increase the rat repelling effect if the interruptions are alsomade to occur in a random manner.

Yet another embodiment of the present invention utilizes a plurality ofspeakers which are sequentially operated to provide the ultrasonicoutput sound levels. By using three such speakers, for example, two ofthe three speakers may constantly be cooling off while the third isoperating.

BRIEF DESCRIPTION OF THE DRAWING The foregoing and other features ofthis invention may more readily be understood by reference to theaccompanying drawing wherein:

FIG. 1 is a block diagram of one embodiment of the present invention;

FIG. 2 is a block diagram of a second embodiment of the presentinvention; and

FIG. 3 is a block diagram of a third embodiment of the presentinvention.

DETAILED DESCRIPTION FIG. 1 depicts a preferred embodiment of thepresent invention. Oscillator 10 is a square wave generator which can beboth amplitude and frequency modulated. Such generators are well knownin the art. Typical of such generators are unijunction relaxationoscillators in which the voltage to the time constant charging resistoris varied in order to achieve frequency modulation, and the Base 2"voltage is varied in order to modulate the amplitude of the output.Sawtooth generator 11 is used to modulate the frequency of the output ofoscillator 10 and signal source 12 is utilized to modulate the amplitudeof the output of oscillator 10. The output of the sawtooth generator 11causes a periodic sweeping of the frequencies generated by oscillator10.

Advantageously, oscillator 10 is caused to produce an output signal, thefrequency of which is periodically swept between approximately 18.5 kHz.and 30 kHz. The range of the frequencies swept may, of course, bemodified somewhat so long as the frequencies are all above the level towhich human beings respond. An upper frequency of about 30 kHz. issufficient, but this upper frequency could also be increased so long asthe frequencies used continue to produce responses in the pests beingeliminated.

The output wave form of oscillator 10 is preferably a square wave. Thewaveform should have quick rise and fall times in order to maximize togeneration of sidebands. If an oscillator is utilized which produces apulse rather than a square wave, the pulse output could be transformedinto a square wave by additional circuitry according to well-knowntechniques. When this approach is utilized, the amplitude modulatingsignal would advantageously be applied to this latter circuitry therebyamplitude modulating the square wave rather than the output of theoscillator. Sawtooth generator 11 may have a period of typically 1 to 10seconds although this period is not critical.

The signal source 12 may advantageously comprise a source for producinga I20 cycle, rectified, sinusoidal signal. It is preferable that theamplitude modulation be applied to the signal in a fairly random mannersince such random modulation aids further in preventing the rat fromadapting to and therefore ignoring the generated sound. Such randommodulation can be achieved by insuring that signal source 12 is notphase locked with sawtooth generator 11. Alternatively, a random noisegenerator could be substituted for source 12, or source 12 could beeliminated altogether if a poorly filtered power supply were used tofeel oscillator 10. It is preferable, however, to use a separate source12 in order to eliminate from other elements of the system the hum whichwould be produced by using a poorly filtered power supply.

The output of oscillator 10 is amplified by amplifier l3 and then fed anemitter follower circuit 14 which is used to drive an electrodynamicspeaker 15. Amplifier 13 may comprise any well-known amplifier capableof amplifying the output signal to a level sufficient to produce thedesired sound level from speaker 15. Emitter follower circuit 14 maycomprise well-known transistor circuitry symbolically shown in FIG. 1.Speaker 15, of the electrodynamic type, can produce an output soundlevel of as much as 120 decibels if it is built with a very stiff coneand has a good heat dissipation construction. Alternatively, speakers ofthe corona type or of the electrostatic type could be utilized.

FIG. 2 depicts another embodiment of the present invention, and elementscommon to both FIGS. 1 and 2 bear the same reference characters. Thecircuit shown in FIG. 2 differs from that in FIG. 1 by the addition of aseries switch 16 and a free-running square wave oscillator 17. Theswitch 16 may, for example, comprise well-known transistor circuitry andis symbolically shown in FIG. 2 as a transistor. Oscillator 17 producesa signal during one-half of each cycle which closes switch 16. Switch 16couples the output signal of output 10 to amplifier 13 only when asignal is present on the base of transistor 16 from oscillator 17. If,for example, oscillator 17 has a period of approximately 100 seconds, aninterrupted output from speaker 15 will be produced which will be on for100 seconds and then off for I seconds. By utilizing such an interruptedoutput, the voice coil of electrodynamic speaker 15 is allowed to coolone-half of the time. This interruption in the output does not appear tohave any detected effect upon the rat-repelling action of the invention.The interruption may, indeed, increase the rat-repelling effect ifoscillator 17 is out of synchronism with both sawtooth generator 11 andsignal source 12.

FIG. 3 depicts yet another embodiment of the present invention. Elementsin FIG. 3 common to FIGS. 1 and 2 bear the same reference characters.FIG. 3 depicts three electrodynamic speakers 15,, 15 and 15 which aresequentially coupled to the output signal of oscillator in order toallow two of the speakers to cool while the third is operating. Anastable multivibrator l8 and three-delay multivibrators 19, 20 and 21,are utilized to sequentially couple to output signal from oscillator 10to the three speakers 15,, and 15 Each of the delay multivibrators 19,and 21, will advantageously have a period equal to one-third of the timeinterval between pulses produced by the astable multivibrator 18. Thus,for example, if astable multivibrator 18 produces pulses every 3seconds, the delay multivibrators will have a period of about I second.

Initially, a signal from multivibrator 18 will energize delaymultivibrator 19. An output signal from multivibrator 19, amplified byamplifier 22, will open switch 23 enabling the output signal fromoscillator 10, amplified by amplifier 24, to pass to amplifier 13, andthence to drive speaker 15, via emitter follower circuitry 14,. After Isecond, delay multivibrator 19 will cease to operate and delaymultivibrator 20 will be energized. The signal from delay multivibrator20, amplified in amplifier 25, will open switch 26 and enable the signalfrom oscillator 10 to drive speaker 15 After another second, delaymultivibrator 20 will cease to operate and delay multivibrator 21 willbe energized. The signal from delay multivibrator 21, amplified inamplifier 27, will open switch 28 and enable the output signal fromoscillator 10 to drive speaker 15 After another second, delaymultivibrator 21 will cease to operate and at this time another pulsewill be produced by astable multivibrator 18 causing the entire sequenceto repeat. In this manner, the speakers, 15,, 15 and 15;, aresequentially coupled to the oscillator 10.

The multivibrators shown in FIG. 3 in block diagram form may compriseany well-known multivibrator circuits capable of performing theoperations described herein. The switches 23, 26, and 28 shown in blockdiagram form, may comprise any of a number of well-known types ofswitches such as wellknown transistor switching circuits. The switchesshown in FIG. 3 as serial switches may alternatively be connected inparallel fashion. Additionally, the signal from oscillator 10 could besequentially coupled to the three speakers 15,, I5, and 15;, by means ofother switching arrangements such as by mechanically operated rotaryswitches.

The period of the multivibrators 18, 19, 20 and 21 is not critical andcould, for example, be designed such that multivibrator 18 is produced apulse at intervals such as 90 seconds with each of the delaymultivibrators then having a period of 30 seconds.

The sound emissions produced in accordance with the present inventionhave been found to be sufficient to cause rats and mice to leave thearea in which the sounds are being produced, although the sound isinaudible to human beings and household pets. It has been found that theinvention is effective in an area up to 10,000 square feet subject tovarious construction barriers, acoustically dampened areas and to theambient sound level. If the ambient sound level at the infested area isbelow the 20 decibel range for atleast 10 to 12 hours out of a 24 hourperiod, it has been found that rats will disappear from the area within72 hours. Although occasional scout" rats may subsequently beoccasionally observed, damage from rats will be effectively eliminated.

Use of the present invention will effectively banish rats from the areain which the invention is used as long as the invention is keptoperational even if used only at night. The modulation applied to thegenerated signal causes the sound to be particularly painful to the ratsand prevents them from building up an immunity to the sound.

The present invention is not designed to kill rats and mice but to drivethem from their habitat. Where the present invention is utilized in aknown infested area, rats will seek an escape from the area within therange of the sound field and will not return so long as the sound isbeing produced. It is advisable that a means of escape be provided forthe rats. If no such escape means is provided, they will run to thefarthest distance from the sound and stay in a huddled position so longas the sound is being produced. During this time they will not be activeand will not eat or drink.

When a rat colony has been forced to leave infested territory because ofuse of the present invention, they will seek another habitat. If theirnewly selected habitat is also rat infested, the invading rats will beattacked by the rats living in the newly selected habitat. This behaviorof rats is described, for example, in an article entitled Rats" by S. A.Barnett appearing at pages 78 through of the Jan., 1967 issue ofScientific American magazine.

This last cited article also documents the reason for the lack ofsuccess in the use of traps baited with food. When rats are living in afamiliar environment, any new food or any other new object is initiallyavoided. Thus, the rats will initially avoid any bait set out for them.Additionally, a strange food avoided at first is later sampled in smallamounts. If it is toxic there is time for the ill effects from a smalldose to develop and the rat thereafter, for many months, will refusesuch bait and anything that tastes like it. Thus, it is apparent thatsuch prior art techniques can never be very successful in eliminatingrats. The present invention, however, achieves the virtual eliminationof these pests within a relatively short period of time.

What have been described are considered to be only illustrativeembodiments of the present invention, and accordingly it is to beunderstood that various and numerous other arrangements can be devisedby one skilled in the art without departing from the spirit and scope ofthis invention.

What is claimed is:

1. An ultrasonic random noise generating apparatus for repelling ratsand mice comprising:

a square wave generator for generating a periodicallyvarying electricsignal within the ultrasonic frequency range; first signal source meansconnected to the generator for repetitiously cycling the frequency ofsaid periodically varying electric signal over a predeterminedultrasonic frequency range;

second signal source means connected to the generator for modulating theamplitude of said periodically varying electric signal out of phase withthe frequency cycling means; and

speaker means coupled to the square wave generator for converting themodulated and cycled periodically varying electric signal to airvibrations.

2. Apparatus according to claim 1 in which the frequency modulatingmeans sweeps the frequency of the generator within the range of 18.5kHz. to 30 kHz.

3. Apparatus according to claim 2 further comprising an amplifiercoupled between the generator and the speaker for amplifying theelectrical signal sufficiently to provide an ultrasonic sound level fromthe speaker ofat least 100 decibels,

4. Apparatus for repelling rats and mice comprising:

an oscillator for generating an electrical signal within the ultrasonicfrequency range;

a sawtooth generator coupled to the oscillator for causing a periodicsweeping of the generated signal within the frequency range of8 l .5kHz. to 30 kl-lz.;

a signal source asynchronous with the sawtooth generator also coupled tothe oscillator for modulating the amplitude of the electrical signal;

a speaker coupled to the oscillator; and

an amplifier coupled between the oscillator and the speaker foramplifying the electrical signal sufficiently to provide an ultrasonicsound level from the speaker of at least 100 decibels.

5. Apparatus according to claim 4 in which the oscillator comprises asquare wave generator.

6. Apparatus according to claim 4 further comprising a switch coupledbetween the oscillator and the speaker and means for repeatedly turningthe switch on and off to effect interruptions in the ultrasonic soundoutput of the speaker.

7. Apparatus according to claim 4 in which the means for repeatedlyturning the switch on and off comprises a square wave oscillator forturning the switch on and off for equal periods of time, the square waveoscillator being asynchronous with both the sawtooth generator and theamplitude modulating signal source.

8. Apparatus for repelling rats and mice comprising:

an oscillator for generating an electrical signal within the ultrasonicfrequency range;

a sawtooth generator coupled to the oscillator for causing a periodicsweeping of the generated signal within the frequency range of 18.5 kHz.to 30 kHz.;

a signal source asynchronous with the sawtooth generator also coupled tothe oscillator for modulating the amplitude of the electrical signal;

a plurality of speakers;

a plurality of switches coupling respective ones of the speakers to theoscillator; and

means for repeatedly and sequentially opening and closing the switches,each switch being opened upon the closing of the next succeeding switch.

9. Apparatus according to claim 8 in which the means for opening andclosing the switches comprises an astable multivibrator coupled to aplurality of delay multivibrators to sequentially energize the delaymultivibrators, each delay multivibrator being coupled to a respectiveone of the switches, each switch being closed responsive to theenergization of its associated delay multivibrator.

10. Apparatus according to claim 9 comprising three switches and threedelay multivibrators and in which each delay multivibrator has a periodequal to one-third of the interval between pulses provided by theastable multivibrator.

11. A method of repelling rats and mice comprising the steps of:

generating an electrical signal within the ultrasonic frequensignal 5 7;V UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION,

Patent No. 3,636,559 Dated Januar 18, 1972 Dominic Del Grande; NorthHolfywood Donald C. Erdman, Pasadena, both of California Inventor(s Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 1, line 37,-after "that" delete "if" and insert "it"; Column 3,line 4, after "fed" insert --to--; I

line 43, after "tl ree" delete the hyphen:

line 44, after "couple" delete "to" and insert "the- Coltimn A, line1.1, after "18'' delete --is--";

Colur nn 5, line 38, delete "claim 4" and insert- '--claim 6'--.

Signed and sealed this 20th day of June 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

1. An ultrasonic random noise generating apparatus for repelling ratsand mice comprising: a square wave generator for generating aperiodically varying electric signal within the ultrasonic frequencyrange; first signal source means connected to the generator forrepetitiously cycling the frequency of said periodically varyingelectric signal over a predetermined ultrasonic frequency range; secondsignal source means connected to the generator for modulating theamplitude of said periodically varying electric signal out of phase withthe frequency cycling means; and speaker means coupled to the squarewave generator for converting the modulated and cycled periodicallyvarying electric signal to air vibrations.
 2. Apparatus according toclaim 1 in which the frequency modulating means sweeps the frequency ofthe generator within the range of 18.5 kHz. to 30 kHz.
 3. Apparatusaccording to claim 2 further comprising an amplifier coupled between thegenerator and the speaker for amplifying the electrical signalsufficiently to provide an ultrasonic sound level from the speaker of atleast 100 decibels.
 4. Apparatus for repelling rats and mice comprising:an oscillator for generating an electrical signal within the ultrasonicfrequency range; a sawtooth generator coupled to the oscillator forcausing a periodic sweeping of the generated signal within the frequencyrange of 81.5 kHz. to 30 kHz.; a signal source asynchronous with thesawtooth generator also coupled to the oscillator for modulating theamplitude of the electrical signal; a speaker coupled to the oscillator;and an amplifier coupled between the oscillator and the speaker foramplifying the electrical signal sufficiently to provide an ultrasonicsound level from the speaker of at least 100 decibels.
 5. Apparatusaccording to claim 4 in which the oscillator comprises a square wavegenerator.
 6. Apparatus according to claim 4 further comprising a switchcoupled between the oscillator and the speaker and means for repeatedlyturning the switch on and off to effect interruptions in the ultrasonicsound output of the speaker.
 7. Apparatus according to claim 4 in whichthe means for repeatedly turning the switch on and off comprises asquare wave oscillator for turning the switch on and off for equalperiods of time, the square wave oscillAtor being asynchronous with boththe sawtooth generator and the amplitude modulating signal source. 8.Apparatus for repelling rats and mice comprising: an oscillator forgenerating an electrical signal within the ultrasonic frequency range; asawtooth generator coupled to the oscillator for causing a periodicsweeping of the generated signal within the frequency range of 18.5 kHz.to 30 kHz.; a signal source asynchronous with the sawtooth generatoralso coupled to the oscillator for modulating the amplitude of theelectrical signal; a plurality of speakers; a plurality of switchescoupling respective ones of the speakers to the oscillator; and meansfor repeatedly and sequentially opening and closing the switches, eachswitch being opened upon the closing of the next succeeding switch. 9.Apparatus according to claim 8 in which the means for opening andclosing the switches comprises an astable multivibrator coupled to aplurality of delay multivibrators to sequentially energize the delaymultivibrators, each delay multivibrator being coupled to a respectiveone of the switches, each switch being closed responsive to theenergization of its associated delay multivibrator.
 10. Apparatusaccording to claim 9 comprising three switches and three delaymultivibrators and in which each delay multivibrator has a period equalto one-third of the interval between pulses provided by the astablemultivibrator.
 11. A method of repelling rats and mice comprising thesteps of: generating an electrical signal within the ultrasonicfrequency range; modulating the frequency of the electrical signal bycausing it to cyclically sweep through a range of frequencies between18.5 kHz. and 30 kHz.; modulating the amplitude of the electrical signalasynchronously with the cyclical sweep; and converting the modulatedsignal to air vibrations of a magnitude sufficient to produce anultrasonic sound level of at least 100 decibels.